(1) Field of the Invention
This invention generally relates to fluid flow measurements and more specifically to a system for testing turbine impellers under transient fluid flow conditions.
(2) Statement of the Prior Art
There are very few existing facilities which can operate a pump or turbine impeller under general and user defined transient conditions throughout the transient. Old facilities operated under either steady-state conditions or specific transient conditions with no provision for defining the desired conditions throughout the transient. Steady-state operation is defined here as when the impeller rotates at constant speed with constant flow rate and pressure rise. Transient operation is defined as when the impeller undergoes acceleration or deceleration (such as at pump start-up or shut down) and the impeller speed, flow rate and pressure rise all change with time.
There are many applications where impellers intentionally operate in a transient mode. However, to date, virtually all transient operation impeller designs are based on quasi steady assumptions and design approaches, i.e. they assume that at any instant in time during a transient, the impeller performance and flow field is identical to that which occurs during the corresponding operation at steady-state rotational speed.
To properly evaluate or eventually optimize a given impeller design, a facility to simulate actual conditions is desirable. Old steady-state facilities could not provide a means of accurately evaluating impeller performance under transient conditions. Old transient test facilities were limited in the type and number of different transient conditions which could be tested. It is thus desirable to have a test facility wherein the impeller speed and flow rate are user definable and controllable throughout the transient and the transient flow rate is accurately measurable.